The present invention is directed to load measuring devices, and more particularly, to load-cell assemblies usable for measuring loads on, as an example, a hospital bed or other frame assembly.
It is frequently desirable to accurately monitor a patient""s weight during the course of a hospital stay. This requires frequent weighing of the patient. However, it is often impractical, if not impossible, to remove patients from a hospital bed to weigh them, particularly on a regular or frequent basis. In order to overcome this difficulty, systems have been designed to weigh patients while they remain in the hospital bed. However, difficulties have been experienced with the accuracy, repeatability, and long-term reliability of existing systems.
Weighing systems have been incorporated into hospital beds, including articulatable hospital beds. Articulatable hospital beds are movable through a wide range of positions as desired by the patient or medical personnel. Movement of the beds exerts various loads and twisting forces on the bed frames. Conventional weighing systems incorporated into hospital beds have experienced difficulty in maintaining accuracy and repeatability because the weighing systems are subjected to significant twisting forces caused by the complex bed construction and the effect of complex movement to certain bed positions. The forces also vary in magnitude depending on the particular configuration of the bed and the position of the patient on the bed. Further, movement of the bed from place to place and frequent change in the bed""s positional configuration makes it extremely difficult to maintain highly accurate results for a weighing system on a bed.
Load-cells have been utilized in hospital beds to accurately weigh the patients while on the bed. The load-cells, however, experience difficulties when the articulatable beds move to certain positions that create complex loads and torque forces on the load cells. Conventional load-cells often bind and/or hang up due to the complex movement, thereby resulting in a hysteresis effect, which decreases the accuracy of determining the patient""s weight while in bed. Further, the load-cells can bind until excessive force releases the load-cell, thereby causing instant movement of the load-cell, which results in extremely inaccurate weight measurements of the patient. Such binding also increases the chance of damaging the load-cell. Accordingly, extreme difficulties have been incurred in utilizing load-cells with articulatable frames, such as bed frames for weighing patients or other masses on the frame.
The present invention overcomes drawbacks experienced by the prior art and provides other benefits. One embodiment of the invention provides a load-cell assembly for use with a frame assembly of, as an example, a hospital bed. The frame assembly is adopted to receive a load thereon. The frame assembly has a first frame and a second frame adjacent to the first frame. The first and second frames are movable relative to each other. The load-cell assembly is positionable to interconnect the first and second frames and to measure the load on the first or second frames. The load-cell assembly includes a load-cell body connectable to the first frame and being substantially stationary relative to the first frame. A stud is attached to the load-cell body and has a free end portion extending away from the load-cell body.
A receiver body is connectable to the second frame and is substantially stationary relative to the second frame. A stud receiver is attached to the receiver body. The stud receiver has an outer portion attached to the receiver body and is substantially non-movable relative to the receiver body. The stud receiver has an inner surface attached to the stud""s free end portion and is substantially non-movable relative to the stud""s free end portion. The stud receiver is at least partially flexible to allow the stud""s free end portion and the stud receiver""s inner surface to move as a unit relative to the receiver body when the first frame moves relative to the second frame. In one embodiment, the receiver body has a cavity formed therein and the stud receiver is retained in the cavity. In one embodiment, the stud receiver is an elastomeric material, such as polyurethane, having a hardness with a durometer value of approximately 90 Shore A.
In one aspect of the invention, the frame assembly, for example, on an articulatable bed assembly is connected to four load-cell assemblies that interconnect the first and second frames. The load-cell assemblies are positioned to fully suspend the first frame relative to the second frame. The load-cell assemblies are adapted to accurately measure the weight of a patient or other mass on the bed portion independent of the position or configuration of the bed.